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K. Qiu, M. Zhang, X. Lu, K. Leung, G. Wang, L. Sun, C.-P. Pang, S. Lam; Diagnostic Classification of Rnfl Measurement in Normal Myopic Subjects: A Comparison Between Time-Domain and Spectral-Domain OCT. Invest. Ophthalmol. Vis. Sci. 2010;51(13):217.
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To evaluate and compare the diagnostic classification of retinal nerve fiber layer (RNFL) measurement between time-domain and spectral-domain optical coherence tomography (OCT) in healthy myopic subjects.
A total of 98 eyes from 98 healthy myopia subjects were included. The parapapillary RNFL was imaged sequentially by Stratus OCT and Cirrus HD OCT (Carl Zeiss Meditec, Dublin, CA) within the same visit. Only images with signal strength of at least 7 were included in the analysis. Diagnostic classification (within normal limits, borderline, or outside normal limits) derived from the 2 OCT instruments were compared with the likelihood ratio chi-square test.
The mean age, axial length, and spherical equivalent were 23± 4.1 years (range, 18-40), 25.54 ±1.31 mm (range, 22.52-28.12), and -4.91± -3.14 D (range, -1 to -12.75), respectively. The respective visual field mean deviation and pattern standard deviation were -2.13 ±1.12 dB and 1.49±0.98 dB. With reference to average RNFL thickness, 96.0% (94/98 eyes) were classified as normal and 4.1% (4/98) as borderline by the Cirrus HD-OCT whereas while all eyes were classified as within normal limits by the Stratus OCT. With reference to sectorial RNFL measurements, the Cirrus HD-OCT identified a significantly higher proportion of eyes as outside normal limits / borderline for at least one clock-hour (Stratus OCT: 14.28% / 35.7%; Cirrus HD-OCT: 21.42% / 52.1%; all with p<0.01). 1 o’clock and 4 o’clock were the most frequent clock hour classified as abnormal (borderline or outside normal limits) by the Cirrus HD-OCT and the Stratus OCT, respectively.
Nasal RNFL measurement was commonly classified as abnormal by Stratus OCT, and more often by Cirrus HD-OCT in myopic eyes. Caution should be exercised in interpreting RNFL measurement in myopic individuals.
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